This invention relates to an apparatus and method for the deposition of thin films onto substrates, semiconductor devices, and other objects and more particularly to such apparatus and method wherein electron-beam induced evaporation techniques are utilized.
The art of vacuum depositing thin polycrystaline and amorphous films of conductors, semiconductors, and insulators by evaporation is well known and highly developed. In such apparatus, heating of the melt material is effected in one of three ways, (1) resistance heating, (2) induction heating, and (3) electron-beam impingement. Resistance heating is quite common and usually involves a resistance heating element embedded in, or wrapped around a cup shaped holder. A crucible, or other container suitably shaped to hold the material to be evaporated is placed within the cup shaped holder and is arranged to transfer heat from this holder to the melt sufficient to cause evaporation. U.S. Pat. No. 3,864,162, issued Feb. 4, 1975 to Kenty, discloses a deposition apparatus that utilizes this type of heating. Induction heating is less common than resistance heating and usually involves an induction coil suitably arranged with respect to the material to be evaporated. An alternating current is used to excite the induction coil thereby inducing heat within the material to be evaporated. Heating by electron-beam impingement, on the other hand, is in widespread use. With this method, a beam of electrons is generated by an electron-beam gun and directed toward the melt by magnetic fields. The electrons impinge upon the surface of the material to be evaporated causing very high localized temperatures. This method of heating offers several advantages over other methods including precise control of the power output of the electron-beam and precise placement thereof and economy of power consumption. For an example of this type of heating device the reader is referred to U.S. Pat. No. 3,996,469 issued Dec. 7, 1976 to James. A variety of high energy particles, such as x-rays, are emitted when the electrons from the electron beam impinge upon the melt. These particles, of course, have direct access to the surface of the device being coated and, under certain circumstances, may alter the characteristics of the device. Therefore, a disadvantage of this type of heating is that its application must be limited to semiconductor devices or other objects that are not sensitive to high energy particles.
As the state-of-the-art in semiconductor technology advances, the new thin film and closely packed monolithic integrated circuit devices are becoming more intolerant to radiation exposed thereto during the manufacturing process. What is needed is an apparatus that prevents these high energy particles from reaching the object being coated during deposition.